How to Winterize Your Sprinkler System So It’s Good as New Come Spring

Gemma Johnstone
Written by Gemma Johnstone
Updated August 1, 2022
Automatic sprinkler system
Photo: georgeclerk / E+ / Getty Images

Purge the pipes to fight the freeze (and big repair bills)

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After a long, hard winter, the idea of seeing your lawn transform to verdant green again is appealing. But, there’s nothing worse than watering your lawn come spring only to find puddles or geysers popping up all over your yard. Taking the proper precautions by winterizing your sprinkler system can help avoid inconvenience and costly sprinkler repairs. Find out how to put your sprinkler pipes on ice before the cold sets.

Why Do I Have to Winterize My Sprinkler System?

When temperatures drop and the ground ices over, if there’s water left in your sprinkler system, the expansion and contraction as it freezes and thaws can cause warping, cracks, and breakages in the pipes and valves. Sprinkler repairs aren’t always straightforward and major problems might result in you having the hassle and expense of replacing the entire system. 

When to Winterize Your Sprinkler System

If you live in a state with year-round balmy weather, you’ll be relieved to hear that this is probably a job you can skip. However, if winter temperatures dip to 32 degrees Fahrenheit or below, you’ll have to be on top of the task before the first expected hard freeze. 

Exact dates depend on regional weather. Typically, it’s a job to do in September or October, but check the forecast and try to be all set at least a week before the frost arrives. Don’t shut it off too early; otherwise, you could develop brown lawn patches if you have a warm, dry fall.

How to Prep Your Sprinkler System for Winterization

Before draining the system, there are a few quick but essential steps to take for safety and seamlessness. 

1. Shut Off the Water Supply

You don’t want water to inadvertently start running through the sprinkler system while you’re working on it. So the first thing you need to do is turn off the sprinkler water supply at the main valve next to your water meter (it’s usually marked as connecting to your sprinkler system and often located in the basement or crawl space). 

Once you’ve located the shut-off lever, turn this perpendicular and test the water supply to the system. If you accidentally select the main water supply lever, it’ll be pretty apparent because it will cut off your entire home’s water supply.

2. Deactivate Timer

If you have an automatic system, turn off the timer using the “off” or “rain mode” setting. This shuts down the signal to the system while keeping your programmed settings like the start time, valve run times, and clock. 

Come spring, just shut off the rain mode, and you should be good to go. To save a bit of energy (about a night light’s worth), you could turn off the power to the controller, but you’ll lose the settings you worked so hard to perfect.

How to Winterize Your Sprinkler System

Once you know no further water can enter the sprinkler system, it’s time to drain the water already in it. You’ll do this using one of three methods. The one you choose depends on the type of system you have, and they vary in complexity. Check the sprinkler system guide you probably have lurking at the bottom of the junk drawer (or do a quick internet search) for more information on your model.

Don’t forget that you're dealing with a pressurized system. So, before you get started on drainage, regardless of type, get your protective eye goggles on.

Manual Draining

If your system allows for manual draining, you’ll be relieved to know it’s a relatively straightforward task involving opening shut–off valves to let the water out using the forces of gravity.

  1. Locate the manual valves at the end of the piping.

  2. Open them one-by-one.

  3. Lift the sprinkler heads to release more water.

  4. Close all the valves once the water stops flowing.

Automatic Draining

If your system has automatic drainage, you can also breathe a sigh of relief, as it’s another relatively painless process. Draining automatically kicks in once the water pressure falls below a certain number of pounds per square inch (psi).

  1. Activate the automatic drain function by briefly running a sprinkler head after the water supply is turned off 

  2. Empty the water that gathers before the shut-off valve inside the backflow devices.

  3. Locate the plastic cap on each of the valves.

  4. Loosen the cap to increase airflow and release any remaining water.

  5. Lift the sprinkler heads to remove any residual water.

Blow Out Draining

This method is the most tricky, and getting it wrong can be hazardous and lead to expensive repairs or injury. It involves forcing the water along the pipes and out of the sprinkler heads with an air compressor. Plus, not every sprinkler system can handle that amount of pressure. When in doubt, call in the pros to handle it.

If you’ve worked with compressed air before and are confident enough to go with the DIY approach, you’ll need the following supplies:

  • A powerful 80 to 100 CFM (cubic feet per minute) rated air compressor

  • Safety goggles

  • A coupler/adapter that fits the compressor to your sprinkler system

The steps below offer guidance for the process, but always check sprinkler model instructions. For example, you can’t blow out pressure vacuum breaker (PVB) and reduced pressure (RP) backflow prevention devices. The heat of the air can cause the rubber seals within them to melt. Most systems have a backflow preventer valve—it’s usually a requirement if your irrigation system connects to your main drinking water supply.

  1. Ensure the mains water supply and backflow preventer valve are both turned off.

  2. Open the hose bib found on the mainline of the sprinkler. Doing this releases pressure on the pipes, removing any air pockets. 

  3. Carefully connect the compressor to the threaded blow out fitting downstream of the backflow device. You might need to use an adapter.

  4. When setting the pressure, don’t go above 80 PSI (pounds per square inch) for rigid PVC piping or 50 PSI for flexible polyethylene piping. Too much pressure can damage or destroy the pipes in the system.

  5. Blow out the zones individually. Start by opening the farthest away zone sprinkler heads.

  6. Open the compressor valve, gradually adding air pressure.

  7. Two short blow out cycles for each zone (of just a couple of minutes) should empty the water while avoiding friction and heat damage. The water will come out the sprinkler head for the zone you have opened the valve to. 

  8. Carefully monitor the pressure during the blow out to ensure it remains below the compressor’s maximum capacity.

  9. Shut off each sprinkler head when it stops emitting water.

  10. Once you have blown out each zone and turned off the air compressor, open and close all the valves on the backflow preventer device. That way, you can release any pressure remaining air in the system.

Tips for Insulating Your Sprinkler System for Extra Protection

Sprinkler in garden
Photo: Mykola Sosiukin / iStock / Getty Images

Adding a layer of insulation to the above-ground parts of your sprinkler system offers extra protection from big freezes. It’s an easy and inexpensive job that’s well worth doing.

Use insulation tape, foam covers, or even pine straw to wrap and cover any exposed pipes, backflow preventers, and the main shut-off valve. Just be careful not to block any air vents or drain outlets. 

DIY vs. Hiring a Pro

If you’re a confident DIYer this is a job you can tackle yourself. Manual and automatic draining are pretty straightforward and don’t require any specialist equipment or technical know-how. To do a blow out, you might just need an appropriate air compressor to do it properly—and you can rent these for as little as $30

However, doing a full blow out is a tricky task to master, and hiring a local sprinkler winterization professional is generally the more sensible course of action. If you're not used to dealing with a high-powered air compressor, you risk suffering from a serious injury or causing damage to your pipes and fittings.  

Expect the average annual cost to winterize your sprinkler system will be between $75 and $150, depending on the number of sprinkler zones you have. This is money well spent compared to spending an average of $250 for the cost to repair your sprinkler system if you don’t winterize it.


How long will it take to winterize my sprinkler system?

You don’t have to worry about this job taking up one of your well-earned days off. It should only take 30 minutes to an hour from start to finish, depending on how many sprinkler zones you have. 

When can I de-winterize my sprinkler system?

Don’t make the mistake of filling the pipes up with water again, only to get taken by surprise with a late hard spring frost. In areas with hard winters, you’re likely using a cool-season grass. These go dormant in the winter and won’t need watering until the ground fully thaws. Even then, you only need to water your lawn sparingly in early spring, and natural rainfall might be enough.

Check the local forecasts for guidance on estimated last frost days in your region and use a shovel to check the ground is easy to pierce and warm before flipping the switches.

What are the key safety considerations when winterizing my sprinkler system?

Safety goggles are a must when draining the system. You’re dealing with high pressure piping and possibly a hazardous air compressor.

You should also move any pets indoors during the blow out process. The pipes often let out high-pitched whistling sounds when emptying, which can spook animals. You don’t want to cause unnecessary stress or risk them scaling the yard fence.

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